U.S. patent application number 11/700708 was filed with the patent office on 2008-05-22 for electrolyte composition for dye-sensitized solar cell, dye-sensitized solar cell including same, and method of preparing same.
Invention is credited to Kwang-Soon Ahn, Jae-Man Choi, Moon-Sung Kang, Moon-Seok Kwon, Jae-Kwan Lee, Ji-Won Lee, Wha-Sup Lee, Soo-Jin Moon, Joung-Won Park, Byong-Cheol Shin.
Application Number | 20080115831 11/700708 |
Document ID | / |
Family ID | 37982483 |
Filed Date | 2008-05-22 |
United States Patent
Application |
20080115831 |
Kind Code |
A1 |
Kang; Moon-Sung ; et
al. |
May 22, 2008 |
Electrolyte composition for dye-sensitized solar cell,
dye-sensitized solar cell including same, and method of preparing
same
Abstract
An electrolyte composition for a dye sensitized solar cell
according to one embodiment includes a first polymer or a
non-volatile liquid compound having a weight average molecular
weight of less than or equal to 500, a second polymer having a
weight average molecular weight of more than or equal to 2000,
inorganic nano-particles, and a redox derivative.
Inventors: |
Kang; Moon-Sung; (Yongin-si,
KR) ; Lee; Ji-Won; (Yongin-si, KR) ; Lee;
Wha-Sup; (Yongin-si, KR) ; Ahn; Kwang-Soon;
(Yongin-si, KR) ; Choi; Jae-Man; (Yongin-si,
KR) ; Lee; Jae-Kwan; (Yongin-si, KR) ; Kwon;
Moon-Seok; (Yongin-si, KR) ; Shin; Byong-Cheol;
(Yongin-si, KR) ; Moon; Soo-Jin; (Yongin-si,
KR) ; Park; Joung-Won; (Yongin-si, KR) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
37982483 |
Appl. No.: |
11/700708 |
Filed: |
January 30, 2007 |
Current U.S.
Class: |
136/263 ;
252/62.2; 977/701 |
Current CPC
Class: |
Y02E 10/547 20130101;
H01G 9/2059 20130101; Y02E 10/542 20130101; H01G 9/2031 20130101;
H01G 9/2004 20130101; Y02P 70/50 20151101 |
Class at
Publication: |
136/263 ;
252/62.2; 977/701 |
International
Class: |
H02N 6/00 20060101
H02N006/00; B01B 1/04 20060101 B01B001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2006 |
KR |
10-2006-0113990 |
Claims
1. An electrolyte composition for a dye sensitized solar cell,
comprising: a first polymer having a weight average molecular
weight of less than or equal to about 500; a second polymer having
a weight average molecular weight of more than or equal to about
2000; and inorganic nano-particles.
2. The composition of claim 1, wherein the first polymer comprises
a liquid-phase polymer.
3. The composition of claim 1, wherein the first polymer comprises
at least one selected from the group consisting of
polyalkyleneoxide, polyacrylonitrile, polyalkylether,
polyalkyleneimine, polyalkylenesulfide, a copolymer of two or more
of the foregoing, and a mixture of two or more of the
foregoing.
4. The composition of claim 1, wherein the first polymer is in an
amount of about 1 to about 95 wt % based on the total weight of the
composition.
5. The composition of claim 1, wherein the second polymer comprises
a solid-phase polymer.
6. The composition of claim 1, wherein the second polymer comprises
at least one selected from the group consisting of
polyalkyleneoxide, polyacrylonitrile, polyalkyleneimine,
polyalkylenesulfide, polyvinylidenehalide, a copolymer of two or
more of the foregoing, and a mixture of two or more of the
foregoing.
7. The composition of claim 1, wherein the second polymer is in an
amount of about 1 to about 20 wt % based on the total weight of the
composition.
8. The composition of claim 1, wherein the inorganic nano-particles
comprise at least one selected from the group consisting of a
carbon-based material, a metal oxide, and a combination
thereof.
9. The composition of claim 8, wherein the carbon-based material
comprises at least one selected from the group consisting of
graphite, denka black, ketjen black, acetylene black, carbon
nanotubes, carbon nanofiber, carbon nanowire, carbon nanoballs,
activated carbon, fullerene, and combinations thereof.
10. The composition of claim 8, wherein the metal oxide comprises
an oxide of one selected from the group consisting of Al, Si, Sn,
Zr, Ti, W, Zn, In, Ba, Nb, Ta, La, Sr, Y, Ho, Bi, Ce, and
combinations thereof.
11. The composition of claim 1, wherein the inorganic
nano-particles have an average particle diameter of less than about
1 .mu.m.
12. The composition of claim 1, wherein the inorganic
nano-particles are in an amount of about 1 to about 30 wt % based
on the total weight of the composition.
13. The composition of claim 1, further comprising a redox
derivative, wherein the redox derivative is configured to produce
an I/I.sub.3.sup.- redox couple.
14. The composition of claim 1, further comprising a volatile
organic solvent selected from the group consisting of acetonitrile,
alcohol, tetrahydrofuran, acetone, dimethylsulfoxide,
dimethylformamide, methoxyacetonitrile, and a mixture of two or
more of the foregoing.
15. The composition of claim 1, wherein the composition is in a
form of a gel.
16. A dye sensitized solar cell, comprising the composition of
claim 1.
17. The solar cell of claim 16, further comprising: a first
electrode; and a second electrode substantially opposing the first
electrode, wherein the composition is interposed between the first
and second electrodes.
18. The solar cell of claim 17, wherein at least one of the first
and second electrodes is substantially transparent.
19. The solar cell of claim 17, further comprising: a first layer
interposed between the first and second electrodes, the first layer
comprising the composition having a first viscosity; and a second
layer interposed between the first layer and the second electrode,
the second layer comprising the composition having a second
viscosity, the second viscosity being different from the first
viscosity.
20. The solar cell of claim 17, wherein the composition has an
increasing viscosity gradient from the first electrode toward the
second electrode.
21. An apparatus comprising the solar cell of claim 16, wherein the
apparatus is selected from the group consisting of external glass
walls of a building or a glass greenhouse.
22. An electrolyte composition for a dye sensitized solar cell,
comprising: a non-volatile non-polymeric liquid compound having a
molecular weight of less than or equal to about 500; a polymeric
compound having a weight average molecular weight of more than or
equal to about 2000; and an inorganic nano-particles.
23. The composition of claim 22, wherein the non-polymeric compound
comprises one selected from the group consisting of alkylene
carbonate, a room temperature molten salt, and a combination
thereof.
24. The composition of claim 23, wherein the room temperature
molten salt comprises an ionic liquid compound comprising
imidazolium.
25. The composition of claim 22, wherein the non-polymeric compound
is in an amount of about 1 to about 95 wt % based on the total
weight of the composition.
26. The composition of claim 22, wherein the polymeric compound
comprises a solid-phase polymer.
27. The composition of claim 22, wherein the polymeric compound
comprises at least one selected from the group consisting of
polyalkyleneoxide, polyacrylonitrile, polyalkyleneimine,
polyalkylenesulfide, polyvinylidenehalide, a copolymer of two or
more of the foregoing, and a mixture of two or more of the
foregoing.
28. The composition of claim 22, wherein the polymeric compound is
in an amount of about 1 to about 20 wt % based on the total weight
of the composition.
29. The composition of claim 22, wherein the inorganic
nano-particles comprise at least one selected from the group
consisting of a carbon-based material, a metal oxide, and a
combination thereof.
30. The composition of claim 29, wherein the carbon-based material
comprises at least one selected from the group consisting of
graphite, denka black, ketjen black, acetylene black, carbon
nanotubes, carbon nanofiber, carbon nanowire, carbon nanoballs,
activated carbon, fullerene, and combinations thereof.
31. The composition of claim 29, wherein the metal oxide comprises
an oxide of one selected from the group consisting of Al, Si, Sn,
Zr, Ti, W, Zn, In, Ba, Nb, Ta, La, Sr, Y, Ho, Bi, Ce, and
combinations thereof.
32. The composition of claim 22, wherein the inorganic
nano-particles have an average particle diameter of less than about
1 .mu.m.
33. The composition of claim 22, wherein the inorganic
nano-particles are in an amount of about 1 to about 30 wt % based
on the total weight of the composition.
34. The composition of claim 22, further comprising a redox
derivative, wherein the redox derivative is configured to produce
an I/I.sub.3.sup.- redox couple.
35. The composition of claim 22, further comprising a volatile
organic solvent selected from the group consisting of acetonitrile,
alcohol, tetrahydrofuran, acetone, dimethylsulfoxide,
dimethylformamide, methoxyacetonitrile, and a mixture of two or
more of the foregoing.
36. The composition of claim 22, wherein the composition is in a
form of a gel.
37. A dye sensitized solar cell, comprising the composition of
claim 22.
38. The solar cell of claim 37, further comprising: a first
electrode; and a second electrode substantially opposing the first
electrode, wherein the composition is interposed between the first
and second electrodes.
39. The solar cell of claim 38, wherein at least one of the first
and second electrodes is substantially transparent.
40. The solar cell of claim 38, further comprising: a first layer
interposed between the first and second electrodes, the first layer
comprising the composition having a first viscosity; and a second
layer interposed between the first layer and the second electrode,
the second layer comprising the composition having a second
viscosity, the second viscosity being different from the first
viscosity.
41. The solar cell of claim 38, wherein the composition has an
increasing viscosity gradient from the first electrode toward the
second electrode.
42. An apparatus comprising the solar cell of claim 37, wherein the
apparatus is selected from the group consisting of external glass
walls of a building or a glass greenhouse.
43. A method of manufacturing a dye sensitized solar cell, the
method comprising: forming a light absorption layer over a first
electrode, the light absorption layer comprising a porous membrane;
providing the composition of claim 1 in or on the light absorption
layer, thereby forming a gel electrolyte; and forming a second
electrode over the gel electrolyte.
44. The method of claim 43, wherein the composition further
comprises a volatile organic solvent selected from the group
consisting of acetonitrile, alcohol, tetrahydrofuran, acetone,
dimethylsulfoxide, dimethylformamide, methoxyacetonitrile, and
combinations thereof, wherein the method further comprises
vaporizing the volatile organic solvent after providing the
composition.
45. The method of claim 43, wherein providing the composition
comprises increasing the viscosity of the composition from the
first electrode toward the second electrode.
46. The method of claim 43, wherein providing the composition
comprises: providing the composition having a first viscosity; and
providing the composition having a second viscosity, the second
viscosity being different from the first viscosity.
47. A method of manufacturing a dye sensitized solar cell, the
method comprising: forming a light absorption layer over a first
electrode, the light absorption layer comprising a porous membrane;
providing the composition of claim 22 in or on the light absorption
layer, thereby forming a gel electrolyte; and forming a second
electrode over the gel electrolyte.
48. The method of claim 47, wherein the composition further
comprises a volatile organic solvent selected from the group
consisting of acetonitrile, alcohol, tetrahydrofuran, acetone,
dimethylsulfoxide, dimethylformamide, methoxyacetonitrile, and
combinations thereof, wherein the method further comprises
vaporizing the volatile organic solvent after providing the
composition.
49. The method of claim 47, wherein providing the composition
comprises increasing the viscosity of the composition from the
first electrode toward the second electrode.
50. The method of claim 47, wherein providing the composition
comprises: providing the composition having a first viscosity; and
providing the composition having a second viscosity, the second
viscosity being different from the first viscosity.
51. The method of claim 43, wherein the second electrode comprises
at least two through-holes.
52. The method of claim 51, which further comprises removing extra
polymer electrolyte through the through-holes after assembling the
first and second electrodes and then sealing the through-holes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 2006-0113990 filed in the Korean
Intellectual Property Office on Nov. 17, 2006, the disclosure of
which is incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] The present disclosure relates to an electrolyte composition
for a dye sensitized solar cell, a dye sensitized solar cell
including the same, and a method for preparing the same. More
particularly, the present disclosure relates to an electrolyte
composition for a dye sensitized solar cell that has excellent ion
conductivity, and can improve stability and durability of a dye
sensitized solar cell, a dye sensitized solar cell including the
same, and a method for preparing the same.
[0004] 2. Description of the Related Technology
[0005] Various research attempts have been carried out to develop
energy sources that can replace conventional fossil fuels and solve
the approaching energy crisis problem. Particularly, extensive
research is underway to find ways for using alternative energy
sources, such as wind power, atomic power, and solar power, as
substitutes for petroleum resources, which are expected to be
depleted within several decades. Among the alternative energy
sources, solar cells use solar energy that is infinite and
environmentally friendly, as opposed to other energy sources. Since
1983 when a Se solar cell was first produced, solar cells have been
highlighted, and Si solar cells have recently been drawing
attention from researchers.
[0006] However, it is difficult to practically use Si solar cells
because the production cost is high and there are difficulties in
improving cell efficiency. To overcome the problem, researchers are
paying attention to a dye sensitized solar cell that can be
produced at a low cost.
SUMMARY
[0007] One embodiment provides an electrolyte composition for a dye
sensitized solar cell having excellent ion conductivity. Another
embodiment provides a dye sensitized solar cell including the
electrolyte composition, and a method for preparing the dye
sensitized solar cell.
[0008] Another embodiment provides an electrolyte composition for a
dye sensitized solar cell, comprising: a first polymer having a
weight average molecular weight of less than or equal to about 500;
a second polymer having a weight average molecular weight of more
than or equal to about 2000; and inorganic nano-particles.
[0009] The first polymer may comprise a liquid-phase polymer. The
first polymer may comprise at least one selected from the group
consisting of polyalkyleneoxide, polyacrylonitrile, polyalkylether,
polyalkyleneimine, polyalkylenesulfide, a copolymer of two or more
of the foregoing, and a mixture of two or more of the foregoing.
The first polymer may be in an amount of about 1 to about 95 wt %
based on the total weight of the composition.
[0010] The second polymer may comprise a solid-phase polymer. The
second polymer may comprise at least one selected from the group
consisting of polyalkyleneoxide, polyacrylonitrile,
polyalkyleneimine, polyalkylenesulfide, polyvinylidenehalide, a
copolymer of two or more of the foregoing, and a mixture of two or
more of the foregoing. The second polymer may be in an amount of
about 1 to about 20 wt % based on the total weight of the
composition.
[0011] The inorganic nano-particles may comprise at least one
selected from the group consisting of a carbon-based material, a
metal oxide, and a combination thereof. The carbon-based material
may comprise at least one selected from the group consisting of
graphite, denka black, ketjen black, acetylene black, carbon
nanotubes, carbon nanofiber, carbon nanowire, carbon nanoballs,
activated carbon, fullerene, and combinations thereof. The metal
oxide may comprise an oxide of one selected from the group
consisting of Al, Si, Sn, Zr, Ti, W, Zn, In, Ba, Nb, Ta, La, Sr, Y,
Ho, Bi, Ce, and combinations thereof. The inorganic nano-particles
have an average particle diameter of less than about 1 .mu.m. The
inorganic nano-particles may be in an amount of about 1 to about 30
wt % based on the total weight of the composition.
[0012] The composition may further comprise a redox derivative,
wherein the redox derivative may be configured to produce an
I/I.sub.3.sup.- redox couple. The composition may further comprise
a volatile organic solvent selected from the group consisting of
acetonitrile, alcohol, tetrahydrofuran, acetone, dimethylsulfoxide,
dimethylformamide, methoxyacetonitrile, and a mixture of two or
more of the foregoing. The composition may be in a form of a
gel.
[0013] Another embodiment provides a dye sensitized solar cell,
comprising the composition described above. The solar cell may
further comprise: a first electrode; and a second electrode
substantially opposing the first electrode, wherein the composition
may be interposed between the first and second electrodes. At least
one of the first and second electrodes may be substantially
transparent.
[0014] The solar cell may further comprise: a first layer
interposed between the first and second electrodes, the first layer
comprising the composition having a first viscosity; and a second
layer interposed between the first layer and the second electrode,
the second layer comprising the composition having a second
viscosity, the second viscosity being different from the first
viscosity. The composition may have an increasing viscosity
gradient from the first electrode toward the second electrode.
[0015] Another embodiment provides an apparatus comprising the
solar cell, wherein the apparatus may be selected from the group
consisting of external glass walls of a building or a glass
greenhouse.
[0016] Yet another embodiment provides an electrolyte composition
for a dye sensitized solar cell, comprising: a non-volatile
non-polymeric liquid compound having a molecular weight of less
than or equal to about 500; a polymeric compound having a weight
average molecular weight of more than or equal to about 2000; and
an inorganic nano-particles.
[0017] The non-polymeric compound may comprise one selected from
the group consisting of alkylene carbonate, a room temperature
molten salt, and a combination thereof. The room temperature molten
salt may comprise an ionic liquid compound comprising imidazolium.
The non-polymeric compound may be in an amount of about 1 to about
95 wt % based on the total weight of the composition.
[0018] The polymeric compound may comprise a solid-phase polymer.
The polymeric compound may comprise at least one selected from the
group consisting of polyalkyleneoxide, polyacrylonitrile,
polyalkyleneimine, polyalkylenesulfide, polyvinylidenehalide, a
copolymer of two or more of the foregoing, and a mixture of two or
more of the foregoing. The polymeric compound may be in an amount
of about 1 to about 20 wt % based on the total weight of the
composition.
[0019] The inorganic nano-particles may comprise at least one
selected from the group consisting of a carbon-based material, a
metal oxide, and a combination thereof. The carbon-based material
may comprise at least one selected from the group consisting of
graphite, denka black, ketjen black, acetylene black, carbon
nanotubes, carbon nanofiber, carbon nanowire, carbon nanoballs,
activated carbon, fullerene, and combinations thereof. The metal
oxide may comprise an oxide of one selected from the group
consisting of Al, Si, Sn, Zr, Ti, W, Zn, In, Ba, Nb, Ta, La, Sr, Y,
Ho, Bi, Ce, and combinations thereof. The inorganic nano-particles
may have an average particle diameter of less than about 1 .mu.m.
The inorganic nano-particles may be in an amount of about 1 to
about 30 wt % based on the total weight of the composition.
[0020] The composition may further comprise a redox derivative,
wherein the redox derivative may be configured to produce an
I/I.sub.3.sup.- redox couple. The composition may further comprise
a volatile organic solvent selected from the group consisting of
acetonitrile, alcohol, tetrahydrofuran, acetone, dimethylsulfoxide,
dimethylformamide, methoxyacetonitrile, and a mixture of two or
more of the foregoing. The composition may be in a form of a
gel.
[0021] Another embodiment provides a dye sensitized solar cell,
comprising the composition described above. The solar cell may
further comprise: a first electrode; and a second electrode
substantially opposing the first electrode, wherein the composition
may be interposed between the first and second electrodes. At least
one of the first and second electrodes may be substantially
transparent.
[0022] The solar cell may further comprise: a first layer
interposed between the first and second electrodes, the first layer
comprising the composition having a first viscosity; and a second
layer interposed between the first layer and the second electrode,
the second layer comprising the composition having a second
viscosity, the second viscosity being different from the first
viscosity. The composition may have an increasing viscosity
gradient from the first electrode toward the second electrode.
[0023] Another embodiment provides a method of manufacturing a dye
sensitized solar cell, the method comprising: forming a light
absorption layer over a first electrode, the light absorption layer
comprising a porous membrane; providing one of the compositions
described above in or on the light absorption layer, thereby
forming a gel electrolyte; and forming a second electrode over the
gel electrolyte.
[0024] The composition may further comprise a volatile organic
solvent selected from the group consisting of acetonitrile,
alcohol, tetrahydrofuran, acetone, dimethylsulfoxide,
dimethylformamide, methoxyacetonitrile, and combinations thereof,
and the method may further comprise vaporizing the volatile organic
solvent after providing the composition.
[0025] Providing the composition may comprise increasing the
viscosity of the composition from the first electrode toward the
second electrode. Providing the composition may comprise: providing
the composition having a first viscosity; and providing the
composition having a second viscosity, the second viscosity being
different from the first viscosity.
[0026] According to another embodiment, an electrolyte composition
for a dye sensitized solar cell is provided. The electrolyte
composition includes a first polymer or a non-volatile liquid
compound having a weight average molecular weight of less than or
equal to about 500, a second polymer having a weight average
molecular weight of more than or equal to about 2000, inorganic
nano-particles, and a redox derivative.
[0027] According to another embodiment, a dye sensitized solar cell
including the electrolyte composition is provided. According to yet
another embodiment, a dye sensitized solar cell is provided. The
dye sensitized solar cell includes a first dye sensitized electrode
disposed on one side of a first electrode, a light absorption layer
disposed on the other side of the first electrode, a second
electrode disposed facing the first electrode, and an electrolyte
disposed between the first and second electrodes. The light
absorption layer includes a porous membrane including semiconductor
particles and a dye adsorbed on the porous membrane.
[0028] According to still another embodiment, a method of
manufacturing a dye sensitized solar cell is provided. The method
includes: forming a light absorption layer including a porous
membrane on which dyes are adsorbed on a first electrode; coating a
polymer gel electrolyte composition including a first polymer or a
non-volatile liquid compound having a weight average molecular
weight of less than or equal to about 500, a second polymer having
a weight average molecular weight of more than or equal to about
2000, inorganic nano-particles, and a redox derivative, on the
light absorption layer to form a polymer gel electrolyte; and
positioning a second electrode on the polymer gel electrolyte
followed by assembling the first and second electrodes. The second
electrode comprises at least two through-holes. The method further
includes removing extra polymer electrolyte through the
through-holes after assembling the first and second electrodes and
then sealing the through-holes
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic cross-sectional view of a dye
sensitized solar cell according to one embodiment.
[0030] FIG. 2 illustrates a manufacturing process of a dye
sensitized solar cell according to one embodiment.
[0031] FIG. 3A is a photograph of electrolyte filled in a solar
cell according to Example 1.
[0032] FIG. 3B is a photograph of electrolyte filled in a solar
cell according to Comparative Example 8.
[0033] FIG. 4A is a SEM photograph showing a cross-section of a
porous membrane of the solar cell according to Example 1.
[0034] FIG. 4B is a SEM photograph showing a cross-section of a
porous membrane of the solar cell according to Comparative Example
4.
[0035] FIG. 5 is a graph showing the photoelectric current-voltage
characteristics of solar cells according to Example 17 and
Comparative Examples 6 and 7.
[0036] FIG. 6 is a graph showing the incident photon-to-current
efficiency (IPCE) of the solar cells according to Example 17 and
Comparative Examples 6 and 7.
[0037] FIG. 7 is a graph showing the current-potential
characteristics of the solar cells according to Example 17 and
Comparative Examples 6 and 7.
[0038] FIG. 8 is a graph showing the incident photon-to-current
efficiency change of solar cells according to Example 10 and
Comparative Example 3.
[0039] FIG. 9 is a graph showing the efficiency change (decrement)
during operations of the solar cells according to Example 10 over
60 days.
DETAILED DESCRIPTION
[0040] An exemplary embodiment will hereinafter be described in
detail with reference to the accompanying drawings.
[0041] Unlike Si solar cells, the dye sensitized solar cell is an
electrochemical solar cell that includes photosensitive dye
molecules and a transition metal. The dye molecules absorb visible
rays and produce electron-hole pairs. The transition metal oxide
transfers the produced electrons. A dye sensitized solar cell may
use nano-titanium oxide, i.e., anatase.
[0042] The dye sensitized solar cell can be produced at a low cost.
Since it can use a transparent electrode, there is an advantage
that it can be applied to external glass walls of a building or a
glass greenhouse. However, the dye sensitized solar cell has a
limitation in application for practical use due to low
photoelectric efficiency.
[0043] The photoelectric efficiency of a solar cell is in
proportion to the quantity of electrons produced from the
absorption of solar beams. Thus, to increase the photoelectric
efficiency, the quantity of electrons should be increased or the
produced and excited electrons should be prevented from being used
to cause electron-hole recombination. The quantity of produced
electrons can be increased by raising the absorption of solar beams
or the dye adsorption efficiency.
[0044] Particles of an oxide semiconductor can be prepared in a
nano-size to increase the dye adsorption efficiency of each unit
area. The reflectivity of a platinum electrode can be increased or
a micro-sized oxide semiconductor light scattering agent can be
included to increase the absorption of solar beams. However, since
such methods have a limitation in increasing the photoelectric
efficiency of solar cells, there is a need to develop new
technology that can improve the photoelectric efficiency.
[0045] A dye sensitized solar cell may include a photoanode
(hereinafter referred to as "a first electrode") including a
semiconductor oxide, a light absorption layer including a porous
membrane and dye molecules adsorbed on the porous membrane, a
counter electrode (hereinafter referred to as "a second electrode")
including a platinum catalyst, and an electrolyte including redox
ion pairs. The composition of the electrolyte may have a large
effect on photoelectric efficiency and durability of a solar
cell.
[0046] A dye sensitized solar cell uses an I.sup.-/I.sub.3.sup.-
redox couple dissolved in an organic solvent such as acetonitrile
for an electrolyte solution. However, the electrolyte solution
including such an organic solvent of the conventional dye
sensitized solar cell may be volatilized when the outer temperature
of the solar cell increases by sunlight. Therefore, this is
disadvantageous for long-term stability and commercialization of
the dye sensitized solar cell. The organic solvent volatilization
decreases the amount of the electrolyte solution. The conductivity
between the two electrodes may deteriorate, decreasing photovoltaic
characteristics and lifespan of a solar cell.
[0047] In order to overcome the above problems, a non-volatile
ionic liquid electrolyte has been suggested since it exists in a
liquid-phase over a wide temperature range. The non-volatile ionic
liquid can prevent problems of electrolyte solution degradation as
a result of organic solvent volatilization. However, electrolyte
leakage may occur during cell fabrication, causing damages to the
cell. This may reduce the solar cell durability. In addition, it
may become difficult to handle the cell.
[0048] As an attempt to solve the problems above, a gel electrolyte
has been suggested. The gel electrolyte can be obtained by
cross-linking or polymerization of polymers using linkable
functional groups of monomers or oligomers. However, such a gel
electrolyte may have problems in that functional groups may remain
by side-reaction or non-reaction after cross-linking or
polymerization. An initiator or a cross-linking agent for
cross-linking and polymerization reactions may also remain in the
electrolyte. These remaining materials in the electrolyte may
deteriorate solar cell voltages or current characteristics.
[0049] In order to transform the liquid electrolyte into the gel
electrolyte, the physical gel electrolyte has been suggested. The
physical gel electrolyte can be obtained by using a matrix of
polymers. The gel electrolyte may solve the problems of the liquid
electrolyte such as volatility or leakage. It may be formed of
polymers and may have an irregular structure. This configuration
may deteriorate the adhesion to the metal oxide layer. Thus, it may
interfere with transmitting electrons generated from the redox
pair, deteriorating the electron conductivity. Further, when the
size of the molecular chain is more than several tens to several
hundred nanometers, it is difficult to transfer it into pores of
the porous layer of the light absorption layer. Therefore, it
generally has low conductivity of less than 10.sup.-6 S/cm.
[0050] According to one embodiment, the electrolyte may be obtained
by mixing a redox ion pair with a first polymer having a weight
average molecular weight of about 500 or less or a non-volatile
liquid mono-molecule and a second polymer having a weight average
molecular weight of about 2000 or more, and adding inorganic
nano-particles to the same to provide a physical gel. The
electrolyte can be easily transmitted into the porous layer of the
light absorption layer and provide higher ion conductivity and
physical strength. It can improve the stability and the durability
of a dye sensitized solar cell.
[0051] An electrolyte composition for a dye sensitized solar cell
according to one embodiment includes a first polymer having a
weight average molecular weight of less than or equal to 500, a
second polymer having a weight average molecular weight of more
than or equal to 2000, inorganic nano-particles, and a redox
derivative. In another embodiment, the composition may include a
non-volatile liquid compound having a molecular weight of less than
or equal to about 500 in place of the first polymer.
[0052] The first polymer or non-volatile liquid compound increases
ion conductivity by dissociating redox ion pairs as well as an
interface area contacting an electrode. It also acts as a
plasticizer to decrease polymer crystallinity.
[0053] The first polymer may have a weight average molecular weight
of less than or equal to about 500. According to one embodiment,
the first polymer may have a weight average molecular weight of
less than or equal to about 250. According to another embodiment,
the first polymer may have a weight average molecular weight
ranging from about 150 to about 200.
[0054] The first polymer may be a colorless, transparent, and
low-viscosity polymer. According to one embodiment, the first
polymer may be present in a liquid-phase. The liquid-phase polymer
has higher ion conductivity (10.sup.-4 to 10.sup.-3 S/cm) than a
solid-phase polymer, and may easily permeate into pores of a porous
membrane of a light absorption layer resulting in improvement of
current density.
[0055] The first polymer may be a polymer including a polar ligand
such as oxygen, nitrogen, sulfur, and so on for dissociating redox
ion pairs. Non-limiting examples of the first polymer may be
selected from the group consisting of polyalkyleneoxide,
polyacrylonitrile, polyalkylether, polyalkyleneimine,
polyalkylenesulfide, copolymers thereof, and combinations thereof.
According to one embodiment, the first polymer may be a polymer
selected from the group consisting of poly(ethyleneoxide),
poly(propyleneoxide), polyacrylonitrile,
poly(ethyleneglycol)dimethylether, polyethyleneimine, polyalkylene
sulfide, a copolymer thereof, and combinations thereof.
[0056] Non-limiting examples of the non-volatile liquid compound
include alkylenecarbonate such as ethylene carbonate, propylene
carbonate, and so on, a room-temperature molten salt, and mixtures
thereof. The room-temperature molten salt may be an ionic salt
compound including imidazolium. The ionic salt exists as a
liquid-phase at room temperature.
[0057] The first polymer or non-volatile liquid compound may be
present in an amount of about 1 to about 95 wt % based on the total
weight of the polymer gel electrolyte composition. According to
another embodiment, the first polymer or non-volatile liquid
compound may be present in an amount of about 25 to about 90 wt %,
optionally about 50 to about 80 wt %.
[0058] The second polymer serves to dissociate redox ion pairs like
the first polymer and improves mechanical properties by electrolyte
gelation. The second polymer may have a weight average molecular
weight of more than or equal to about 2000. According to one
embodiment, the second polymer may have a weight average molecular
weight of about 5000 to about 1,000,000. The second polymer may be
a solid-phase polymer that can act as a matrix in an electrolyte
and improve mechanical strength of an electrolyte.
[0059] The second polymer may be a polymer without a polar ligand
such as oxygen, nitrogen, sulfur, and so on for dissociating redox
ion pairs. Non-limiting examples of the second polymer may be
selected from the group consisting of polyalkyleneoxide,
polyacrylonitrile, polyalkyleneimine, polyalkylenesulfide,
polyvinylidenehalide, copolymers thereof, and combinations thereof.
According to one embodiment, the second polymer may be a polymer
selected from the group consisting of poly(ethyleneoxide),
poly(propyleneoxide), polyacrylonitrile, polyethyleneimine,
polyalkylene sulfide, polyvinylidene fluoride, copolymers thereof,
and combinations thereof.
[0060] The second polymer may be present in an amount of about 1 to
about 20 wt % based on the total weight of the polymer gel
electrolyte composition. According to one embodiment, the second
polymer may be present in an amount of about 5 to about 15 wt
%.
[0061] The inorganic nano-particles serve to decrease polymer
crystallinity, and increase ion conductivity, thereby preventing
ion conductivity decrease due to gelation. They also increase
photovoltaic current of a solar cell by increasing sunlight
scattering.
[0062] The inorganic nano-particles may be formed of at least one
material selected from the group consisting of carbon-based
materials, a metal oxide, and combinations thereof. Non-limiting
examples of the carbon-based materials include graphite, denka
black, ketjen black, acetylene black, carbon nanotubes, carbon
nanofiber, carbon nanowire, carbon nanoballs, activated carbon,
fullerene, and combinations thereof. The metal oxide may be oxide
of an element selected from the group consisting of Al, Si, Sn, Zr,
Ti, W, Zn, In, Ba, Nb, Ta, La, Sr, Y, Ho, Bi, Ce, and combinations
thereof. According to one embodiment, the metal oxide may be
TiO.sub.2, SnO.sub.2, SiO.sub.2, WO.sub.3, ZnO, BaTiO.sub.3,
Nb.sub.2O.sub.5, In.sub.2O.sub.3, ZrO.sub.2, Ta.sub.2O.sub.5,
La.sub.2O.sub.3, SrTiO.sub.3, Y.sub.2O.sub.3, Ho.sub.2O.sub.3,
CeO.sub.2, Al.sub.2O.sub.3, or zeolite. According to another
embodiment, the metal oxide may be selected from the group
consisting of TiO.sub.2, SnO.sub.2, SiO.sub.2, and zeolite.
TiO.sub.2 has excellent ion adsorption characteristics on a surface
of the nano-particle surface.
[0063] As the specific surface area of an inorganic nano-particle
is larger, more cations are adsorbed on the particle surface and
thereby can provide more anion transferring paths. The inorganic
nano-particles may have an average particle diameter of less than
about 1 .mu.m. According to one embodiment, the inorganic
nano-particles have an average particle diameter of more than or
equal to about 10 nm and less than about 1 .mu.m According to
another embodiment, the inorganic nano-particles have an average
particle diameter of about 10 nm to about 100 nm, optionally about
20 to about 30 nm.
[0064] In one embodiment, the inorganic nano-particles may have a
white color. In the case that the inorganic nano-particles are
white, a light scattering effect can be more improved and thereby
re-utilization of light can be improved in a solar cell.
[0065] The inorganic nano-particles may be present in an amount of
about 1 to about 30 wt % based on the total weight of the polymer
gel electrolyte. According to one embodiment, the inorganic
nano-particles may be present in an amount of about 5 to about 15
wt %.
[0066] The redox derivative serves to continuously transfers
electrons between the first and second electrodes by a reversible
oxidation-reduction reaction in an electrolyte. More specifically,
the redox derivative performs an oxidation-reduction reaction,
using electrons transferred from an electrode, and transfers the
electrons to a dye at a ground energy state, thereby generating a
current.
[0067] The redox derivative is a material configured to provide a
redox couple. Examples of the redox derivative include, but are not
limited to, a metal halide salt such as lithium iodide, sodium
iodide, potassium iodide, lithium bromide, sodium bromide, or
potassium bromide; and an iodide of a nitrogen-containing
heterocyclic compound such as imidazolium salts, pyridinium salts,
quaternary ammonium salts, pyrrolidinium salts, pyrazolidium salts,
isothiazolidium salts, isoxazolidium salts, and so on.
[0068] Examples of the iodide of the nitrogen-containing
heterocyclic compound include 1-methyl-3-propyl imidazolium iodide,
1-methyl-3-isopropyl imidazolium iodide, 1-methyl-3-butyl
imidazolium iodide, 1-methyl-3-isobutyl imidazolium iodide,
1-methyl-3-s-butylimidazolium iodide, 1-methyl-3-pentyl imidazolium
iodide, 1-methyl-2-isopentyl imidazolium iodide, 1-methyl-2-hexyl
imidazolium iodide, 1-methyl-3-isohexylimidazolium iodide,
1-methyl-3-ethyl imidazolium iodide, 1,2-dimethyl-3-propylimidazole
iodide, pyrrolidinium iodide, and so on.
[0069] The redox derivative is configured to provide an
I.sup.-/I.sub.3.sup.- redox couple. For example, the
I.sup.-/I.sub.3.sup.- redox couple may be prepared by dissolving
iodine in an iodide molten salt or iodine or iodide in a molten
salt of a compound except iodide.
[0070] The polymer gel electrolyte composition according to one
embodiment can further include a volatile organic solvent selected
from the group consisting of acetonitrile, alcohol,
tetrahydrofuran, acetone, dimethylsulfoxide, dimethylformamide,
methoxyacetonitrile, and combinations thereof. The volatile organic
solvent increases solubility of the redox couple and decreases
viscosity increment by a polymer addition. However, the volatile
organic solvent may be volatilized during operation of a dye
sensitized solar cell, causing electrolyte loss and conductivity
decrease. Therefore, in one embodiment, the volatile organic
solvent can be volatilized during fabrication of a dye sensitized
solar cell.
[0071] The volatile organic solvent may be present in an amount of
less than or equal to about 30 wt % based on the polymer
electrolyte gel composition. According to one embodiment, the
volatile organic solvent may be present in an amount of about 10 to
about 20 wt %.
[0072] The polymer gel electrolyte composition does not include a
polymer polymerization initiator, a cross-linking agent, and so on.
It is a physical gel that is formed by the solid-phase second
polymer. The polymer gel electrolyte composition easily permeates
into the pores of the light absorption layer, and also provides
high ion conductivity and mechanical strength.
[0073] According to another embodiment, a dye sensitized solar cell
including the polymer gel electrolyte composition as an electrolyte
can be described. FIG. 1 is a cross-sectional view showing a
structure of a dye sensitized solar cell in accordance with one
embodiment.
[0074] Referring to FIG. 1, the dye sensitized solar cell 10 may
have a sandwich structure. The structure includes two plate-shaped
transparent electrodes: a first electrode 11 and a second electrode
14 facing each other. The light absorption layer 12 is disposed on
the surface of the first electrode 11, facing the second electrode
14. A space between the two electrodes 11 and 14 is filled with an
electrolyte 13. The light absorption layer 12 may include a porous
membrane (not shown) including semiconductor particles and dye
molecules adsorbed to the porous membrane.
[0075] During operation, solar beams enter the dye sensitized solar
cell, and dye molecules in the light absorption layer 12 absorb
photons. The dye molecules that have absorbed photons are excited
from a ground state, which is called electron transfer, thereby
forming electron-hole pairs. The excited electrons are injected
into a conduction band on the semiconductor particle interface. The
injected electrons are transferred to the first electrode 11
through the interface and then they are transferred to the second
electrode 14 through an external circuit. The dye that is oxidized
as a result of the electron transfer is reduced by ions of an
oxidation-reduction couple in the electrolyte 13. The oxidized ions
are involved in a reduction reaction with electrons that have
arrived at the interface of the second electrode 14 to achieve
charge neutrality.
[0076] In one embodiment, the first electrode (working electrode,
semiconductor electrode) 11 may include a transparent substrate and
a conductive layer disposed on the transparent substrate. The
transparent substrate may be formed of any transparent material to
transmit external light, such as glass or a plastic material.
Non-limiting examples of the plastic material may include
polyethyleneterephthalate (PET), polyethylene naphthalate (PEN),
polycarbonate (PC), polypropylene (PP), polyimide (PI), triacetyl
cellulose (TAC), and polymers thereof. The transparent substrate
may be doped with a doping material selected from the group
consisting of Ti, In, Ga, and Al.
[0077] A conductive layer may be disposed on the transparent
substrate. The conductive layer may include a conductive metal
oxide selected from the group consisting of indium tin oxide (TO),
fluorine tin oxide (FTO), ZnO--(Ga.sub.2O.sub.3 or
Al.sub.2O.sub.3), a tin-based oxide, antimony tin oxide (ATO), zinc
oxide, and combinations thereof. SnO.sub.2 or ITO may be suitable
since they have excellent conductivity, transparency, and heat
resistance. The conductive layer may include a mono-layered or a
multi-layered conductive metal oxide.
[0078] The light absorption layer 12 may be formed on the first
electrode 11. The light absorption layer 12 may include a porous
membrane including semiconductive particles and a photosensitive
dye adsorbed on the surface of the porous membrane. The porous
membrane has very minute and uniform nano-pores, and includes
semiconductor particles having a very minute and uniform average
particle size. The semiconductor particles may be of an elementary
substance semiconductor, which is represented by silicon, a
compound semiconductor, or a perovskite compound.
[0079] The semiconductor may be an n-type semiconductor in which
electrons of the conduction band become a carrier by being
optically excited and provide an anode current. Examples of the
compound semiconductor include an oxide including at least one
metal selected from the group consisting of Ti, Zr, Sr, Zn, In, Yr,
La, V, Mo, W, Sn, Nb, Mg, Al, Y, Sc, Sm, Ga, In, and TiSr.
According to one embodiment, the compound semiconductor may be
TiO.sub.2, SnO.sub.2, ZnO, WO.sub.3, Nb.sub.2O.sub.5, TiSrO.sub.3,
or mixtures thereof. According to another embodiment, the compound
semiconductor may be anatase TiO.sub.2. The semiconductor is not
limited to the above-mentioned materials, and the above-mentioned
materials may be used individually or in combination. The
semiconductor particles may have a large surface area to allow the
dye adsorbed onto the surface of the semiconductor particles to
absorb much light.
[0080] The porous membrane may be fabricated in accordance with any
conventional method of fabricating a porous membrane. According to
one embodiment, it may be fabricated according to a mechanical
necking treatment in which the membrane density of the porous
membrane is controlled by suitably adjusting treatment
conditions.
[0081] The surface of the porous membrane adsorbs the dye that
absorbs external light and produces excited electrons. The dye may
be a metal composite including at least one selected from the group
consisting of aluminum (Al), platinum (Pt), palladium (Pd),
europium (Eu), lead (Pb), iridium (Ir), ruthenium (Ru), and the
like. Since the ruthenium belongs to a platinum-based element and
can form many organic metal composites, the ruthenium can be used
as a dye. An organic dye such as coumarin, porphyrin, xanthene,
riboflavin, triphenyl methane, and so on can be also used.
[0082] In the above description, the light absorption layer 12 has
a two-layered structure composed of the porous membrane including
semiconductive particles and the dye adsorbed on the porous
membrane, but it may have a mono-layered structure by the solvent
washing process further included after obtaining the light
absorption layer. In one embodiment, the light absorption layer 12
may have a thickness of about 15 .mu.m or less. According to
another embodiment, the thickness ranges from about 1 to about 15
.mu.m.
[0083] A second electrode (counter electrode) 14 is formed to
substantially oppose the first electrode 11 with the light
absorption layer 12 interposed therebetween. The second electrode
14 may include a transparent substrate and a transparent electrode
facing the first electrode 11, and a catalyst electrode (not shown)
formed on the transparent substrate.
[0084] The transparent substrate may be formed of a glass or a
plastic material as the first electrode. Examples of the plastic
include polyethylene terephthalate, polyethylene naphthalate,
polycarbonate, polypropylene, polyimide, triacetylcellulose, and so
on.
[0085] The transparent electrode is disposed on the transparent
substrate. The transparent electrode may be formed of a transparent
material such as indium tin oxide, fluorine tin oxide, antimony tin
oxide, zinc oxide, tin oxide, ZnO--Ga.sub.2O.sub.3,
ZnO--Al.sub.2O.sub.3, and so on. The transparent electrode may
include a mono-layered membrane or a multi-layered membrane.
[0086] The catalyst electrode is disposed on the transparent
electrode. The catalyst electrode serves to activate a redox
couple, and includes a conductive material selected from the group
consisting of platinum (Pt), gold (Au), ruthenium (Ru), palladium
(Pd), rhodium (Rh), iridium (Ir), osmium (Os), carbon (C),
WO.sub.3, TiO.sub.2, and a conductive polymer.
[0087] In one embodiment, the catalyst electrode may be porous to
increase the surface area so that the catalyst effect is improved.
For example, Pt or Au may have a black state (herein, "black state"
is referred to as the state in which nothing is supported on the
supported body), and carbon may have a porous state. Particularly,
the platinum black state may be obtained by a sputtering method, a
chloroplatinic acid method, and so on. Further, porous carbon may
be obtained by sintering carbon particles or firing organic
polymers.
[0088] The second electrode 14 includes a through-hole (not shown)
penetrating the second electrode. The through-hole allows an extra
electrolyte 13 to exit from the solar cell when the first electrode
11 is combined with the second electrode 14. This configuration
permits filling the electrolyte without producing pores or air
bubbles inside the solar cell. In another embodiment, more than two
through-holes may be formed in the second electrode 14 in order to
guide the extra electrolyte to the outside. According to another
embodiment, more than three through-holes are formed. After the
first electrode 11 is combined with the second electrode 14, the
hole is sealed with an adhesive material and a cover glass.
[0089] As described above, the electrolyte 13 is interposed between
the first electrode 11 and the second electrode 14. In the
embodiment described above, the electrolyte 13 may be substantially
uniformly dispersed inside the porous membrane of the light
absorption layer 12.
[0090] The electrolyte 13 may include the same polymer gel
electrolyte composition as mentioned above. The electrolyte 13 may
be a mono-layer of the polymer gel electrolyte having the same
viscosity, or a multi-layer thereof having an increasing viscosity
from the first electrode 11 toward the second electrode 14.
[0091] According to another embodiment, the electrolyte in the
porous membrane of the light absorption layer 12 has a lower
viscosity than that of the electrolyte interposed between the
porous membrane and the second electrode 14. This configuration
facilitates transmitting the electrolyte into pores of the porous
membrane.
[0092] According to yet another embodiment, the viscosity of the
electrolyte in the porous membrane may be about 10 to about 100
times lower than that of the electrolyte interposed between the
porous membrane and the second electrode 14.
[0093] The dye sensitized solar cell 10 may be fabricated using a
method including: providing a light absorption layer 12 on a first
electrode 11. The light absorption layer 12 can include a porous
membrane with a dye adsorbed therein. The method further includes
coating the light absorption layer 12 with a polymer gel
electrolyte composition. The composition includes a first polymer
having a weight average molecular weight of about 500 or less or a
non-volatile liquid single molecule, a second polymer having a
weight average molecular weight of about 2000 or more, inorganic
nano-particles, and a redox derivative to provide a polymer gel
electrolyte 13. The method also includes placing a second electrode
14 on the polymer gel electrolyte so as to face the first electrode
11. It will be appreciated that various methods can be adapted for
fabricating a solar cell having the aforementioned structure.
[0094] In another embodiment, the polymer gel electrolyte may be
provided while generating a viscosity gradient between the first
and second electrodes. For example, a lower viscosity composition
may be provided first, and then a higher viscosity composition may
be provided sequentially, or vice versa. This configuration
facilitates transmitting the lower viscous polymer gel electrolyte
composition into pores of the porous membrane and to provide a
higher viscous polymer gel electrolyte composition on the porous
membrane with excellent mechanical strength.
[0095] FIG. 2 shows a manufacturing process of the dye sensitized
solar cell according to another embodiment, including different
viscosity electrolytes. As shown in FIG. 2, a light absorption
layer 12 is formed on a first electrode (S1). The first electrode
11 may be the same as mentioned above, and may be fabricated in
accordance with any suitable manufacturing method. For example, the
first electrode 11 may be obtained by forming a conductive layer
including a conductive material on a transparent substrate in
accordance with an electroplating or a sputtering process, an
electron beam depositing process, and so on.
[0096] A porous membrane is formed on the first electrode 11, and a
dye molecule is adsorbed in the porous membrane to provide a light
absorption layer 12. The porous membrane may be obtained by
dispersing the semiconductor particles into a solvent such as
alcohol, water, and so on to provide a composition for a porous
membrane; coating the composition on the first electrode in
accordance with any suitable coating process; and heating or
mechanically necking the same.
[0097] Subsequently, the porous membrane is sprayed, coated, or
immersed with a dispersion solution including a dye to adsorb the
dye in the porous membrane. The dye can be adsorbed on the surface
of the semiconductive particles in the porous membrane by immersing
the porous membrane into a dispersion solution containing the dye
for about 12 hours. Herein, the dye may be the same as mentioned
above. The solvent is not limited, but may include acetonitrile,
dichloromethane, an alcohol-based solvent, and so on. Further, the
dispersion solution including the dye may further include various
organic colorants to improve the absorption of long wavelength
visible light. After forming the dye layer, it is washed with a
solvent to provide a mono-layer of a light absorption layer 12.
[0098] The first polymer gel electrolyte composition having a lower
viscosity is coated on the obtained light absorption layer 12 to
provide a first polymer gel electrolyte 13a (S2). The first polymer
gel electrolyte composition may be the same as mentioned above. The
first polymer gel electrolyte 13a may have a lower viscosity such
as about 10 cP to about 50 cP in order to facilitate transmitting
the same into pores of the porous membrane. According to another
embodiment, the viscosity may range from about 10 cP to about 30
cP. Such range of the viscosity of the first polymer gel
electrolyte may be suitably adjusted depending upon amounts of the
first polymer or the non-volatile organic solvent.
[0099] The first polymer gel electrolyte composition can be coated
using a method selected from the group consisting of screen
printing, spray coating, doctor blade coating, gravure coating, dip
coating, silk screening, painting, slot die coating, spin coating,
and combinations thereof. The coating method can be selected
depending on the composition viscosity. According to one
embodiment, doctor blade coating may be used since the composition
can be coated in a uniform thickness on a porous membrane.
[0100] After the first polymer gel electrolyte 13a is formed, a
higher viscosity polymer gel electrolyte composition is coated to
provide a second polymer gel electrolyte 13b (S3). The polymer gel
electrolyte composition may be the same as mentioned above.
However, according to another embodiment, the second polymer gel
electrolyte 13b may have a viscosity ranging from about 100 cP to
about 5000 cP in order to provide excellent mechanical strength.
According to another embodiment, the viscosity ranges from about
500 cP to about 3000 cP. Such viscosity control of the second
polymer gel electrolyte may be suitably adjusted depending upon
amounts of the first polymer and the second polymer or the
non-volatile organic solvent. The higher viscosity polymer gel
electrolyte composition may be coated in accordance with the
above-mentioned method.
[0101] After coating the first or the second polymer gel
electrolyte composition, it may further include volatilizing
volatile organic solvents included in the first or the second
polymer gel electrolyte. The volatilizing process is carried out by
spontaneous evaporation or vacuum drying. Thereby, air bubble or
pore formation may be prevented from increasing the contact
interface between the polymer gel electrolyte and the second
electrode.
[0102] In addition, the second electrode 14 is prepared and
disposed on the second polymer gel electrolyte 13b. Then, it is
combined with the first electrolyte 11 (S4) to provide a dye
sensitized solar cell (S5). The second electrode 14 may include a
transparent substrate, a transparent electrode, and a catalyst
electrode as mentioned above, and may be fabricated in accordance
with any conventional method.
[0103] The first electrode 11 may be combined with the second
electrode 14 by any suitable method. For example, the first
electrode 11 may be combined with the second electrode 14 by using
an adhesive material. The adhesive material 15 may include a
thermoplastic polymer film such as one of the trade name Surlyn
(available from E. I. du Pont de Nemours and Company). The
thermoplastic polymer film is disposed between two electrodes and
hot-pressed, which seals them. The adhesive material may further
include epoxy resins or an ultraviolet ray (UV) hardening agent.
Herein, it is hardened after carrying out the heat treatment or UV
treatment.
[0104] When the first electrode 11 and the second electrode 14 are
hot-pressed, the extra electrolyte 13 overflows through the
through-hole 16 of the second electrode 14. Thereby, the
electrolyte can be substantially uniformly filled without
generating pores inside the solar cell by guiding the extra
electrolyte to the outside through the through-hole.
[0105] The dye sensitized solar cell fabricated by the above
mentioned process includes a polymer gel electrolyte, and thus it
can improve the cell stability and durability. The following
examples illustrate the present disclosure in more detail. However,
it is understood that the present disclosure is not limited by
these examples.
EXAMPLE 1
[0106] 1.20M 1-propyl-3-methylimidazolium iodide and 0.12M iodine
were dissolved in a solvent of poly(ethyleneglycol)dimethylether
(PEGDME, weight average molecular weight: 250 /mol) to prepare a
mixed solution. 10 wt % of polyethylene oxide (weight average
molecular weight 1,000,000 g/mol) was added to the mixed solution
and then agitated. Next, 10 wt % of titanium oxide nano-particles
(P-25, average particle diameter: 30 nm, available from Degussa
Corp., Duisseldorf, Germany) were added to the solution and
dispersed by agitating and ultra-sonication grinding to prepare a
polymer gel electrolyte composition having a viscosity of 1800
cP.
[0107] 30 wt % of TiO.sub.2 semiconductor particles having an
average particle diameter of 20 nm were dispersed in 100 ml of
acetylacetone to prepare a composition for a porous membrane. The
composition was coated using a doctor blade at a rate of 5 mm/sec
on a transparent glass substrate having a substrate resistance of
10 .OMEGA./.quadrature. on which indium tin oxide (indium doped tin
oxide) was coated. Drying and pressing were performed to form a
porous membrane including TiO.sub.2. The porous membrane had a
thickness of 0.035 mm.
[0108] The first electrode on which the porous membrane was formed
was dipped in a 0.3 mM ruthenium
(4,4-dicarboxyl-2,2'-bipyridine).sub.2(NCS).sub.2 solution for 24
hours to adsorb the dyes on the porous membrane. The porous
membrane on which the dyes were adsorbed was washed with
ethanol.
[0109] The polymer gel electrolyte composition was coated on the
first electrode including the porous membrane thereon to form an
electrolyte layer. Volatile organic solvents in the polymer gel
electrolyte composition were volatilized by drying under
vacuum.
[0110] Transparent glass substrate having a substrate resistance of
10 .OMEGA./.quadrature. on which indium tin oxide was coated was
deposited with platinum by sputtering to form a catalyst electrode
with a surface resistance of 0.5.OMEGA.. Thereby, a second
electrode was fabricated. Through-holes penetrating the second
electrode were formed by a drill bit having a diameter of 0.75
mm.
[0111] The electrolyte on the first electrode was arranged to face
the second electrode and then a 60 .mu.m-thick thermoplastic
polymer film was positioned between the transparent substrates of
the first and second electrodes. The first and second electrodes
were subjected to hot-pressing at 80.degree. C. for 9 seconds to
assembly the first and second electrodes.
[0112] Extra electrolyte was removed through the through-holes of
the second electrode and then the through-holes of the second
electrode were sealed to fabricate a dye sensitized solar cell.
EXAMPLE 2
[0113] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 500 g/mol was used to prepare a polymer gel electrolyte
composition having a viscosity of 1900 cP.
EXAMPLE 3
[0114] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that ethylenecarbonate
(molecular weight: 88.1 g/mol) non-volatile liquid compound was
used to prepare a polymer gel electrolyte composition having a
viscosity of 1700 cP (at 25.degree. C.) instead of
poly(ethyleneglycol)dimethylether.
EXAMPLE 4
[0115] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 500 g/mol and carbon nanotubes (average particle
diameter: 30 nm) instead of titanium oxide nano-particles were used
to prepare a polymer gel electrolyte composition having a viscosity
of 1800 cP.
EXAMPLE 5
[0116] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 500 g/mol and indium tin oxide (average particle
diameter: 30 nm) were used to prepare a polymer gel electrolyte
composition having a viscosity of 1800 cP.
EXAMPLE 6
[0117] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 500 g/mol and titanium oxide nano-particles (JA-01
available from Tayca Corp., Japan, average particle diameter: 180
nm) were used to prepare a polymer gel electrolyte composition
having a viscosity of 1800 cP.
EXAMPLE 7
[0118] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 500 g/mol and titanium oxide nano-particles (synthesized
particle, average particle diameter: 10 nm) were used to prepare a
polymer gel electrolyte composition having a viscosity of 1900
cP.
EXAMPLE 8
[0119] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 500 g/mol and titanium oxide nano-particles (synthesized
particle, average particle diameter: 100 nm) were used to prepare a
polymer gel electrolyte composition having a viscosity of 1900
cP.
EXAMPLE 9
[0120] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 500 g/mol and titanium oxide nano-particles (synthesized
particle, average particle diameter: 1 .mu.m) were used to prepare
a polymer gel electrolyte composition having a viscosity of 1600
cP.
EXAMPLE 10
[0121] 1.20M 1-propyl-3-methylimidazolium iodide and 0.12M iodine
(I.sub.2) were dissolved in a solvent of
poly(ethyleneglycol)dimethylether (PEGDME, weight average molecular
weight 250 /mol) to prepare a mixed solution. 10 wt % of
polyethylene oxide (weight average molecular weight 1,000,000
g/mol) was added to the mixed solution and then agitated. 10 wt %
of titanium oxide nano-particles (P-25, average particle diameter:
30 nm, available from Degussa Corp.) and 20 wt % of acetonitrile
were added to the solution and dispersed by agitating and
ultra-sonication grinding to prepare a polymer gel electrolyte
composition having a viscosity of 1000 cP. Using the polymer gel
electrolyte composition, the dye sensitized solar cell was
fabricated according to the same method as in Example 1.
EXAMPLE 11
[0122] The dye sensitized solar cell was fabricated according to
the same method as in Example 10, except that the titanium oxide
nano-particles were used in an amount of 1 wt % to prepare a
polymer gel electrolyte composition having a viscosity of 1200
cP.
EXAMPLE 12
[0123] The dye sensitized solar cell was fabricated according to
the same method as in Example 10, except that the titanium oxide
nano-particles were used in an amount of 5 wt % to prepare a
polymer gel electrolyte composition having a viscosity of 1100
cP.
EXAMPLE 13
[0124] The dye sensitized solar cell was fabricated according to
the same method as in Example 10, except that the titanium oxide
nano-particles were used in an amount of 20 wt % to prepare a
polymer gel electrolyte composition having a viscosity of 920
cP.
EXAMPLE 14
[0125] The dye sensitized solar cell was fabricated according to
the same method as in Example 10, except that the titanium oxide
nano-particles were used in an amount of 30 wt % to prepare a
polymer gel electrolyte composition having a viscosity of 850
cP.
EXAMPLE 15
[0126] The dye sensitized solar cell was fabricated according to
the same method as in Example 10, except that the titanium oxide
nano-particles were used in an amount of 15 wt % to prepare a
polymer gel electrolyte composition having a viscosity of 1000
cP.
EXAMPLE 16
[0127] The dye sensitized solar cell was fabricated according to
the same method as in Example 10, except that the titanium oxide
nano-particles were used in an amount of 40 wt % to prepare a
polymer gel electrolyte composition having a viscosity of 800
cP.
EXAMPLE 17
[0128] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 400 g/mol was used to prepare a polymer gel electrolyte
composition having a viscosity of 2000 cP.
EXAMPLE 18
[0129] 1.20M 1-propyl-3-methylimidazolium iodide and 0.12M iodine
were dissolved in a solvent of poly(ethyleneglycol)dimethylether
(PEGDME, weight average molecular weight: 250 /mol) to prepare a
mixed solution. 10 wt % of polyethylene oxide (weight average
molecular weight 1,000,000 g/mol) was added to the mixed solution
and then agitated. 10 wt % of titanium oxide nano-particles (P-25,
average particle diameter: 30 nm, available from Degussa Corp.) and
20 wt % of acetonitrile were added to the solution and dispersed by
agitating and ultra-sonication grinding to prepare a first polymer
gel electrolyte composition having a viscosity of 25 to 30 cP.
[0130] A second polymer gel electrolyte composition was prepared
according to the same method as the first polymer gel electrolyte
composition, except that 5 wt % of acetonitrile was used.
[0131] 30 wt % of TiO.sub.2 semiconductor particles having an
average particle diameter of 20 nm were dispersed in 100 ml of
acetylacetone to prepare a composition for a porous membrane. The
composition was coated using a doctor blade at a rate of 5 mm/sec
on a transparent glass substrate having a substrate resistance of
10 .OMEGA./.quadrature. on which indium tin oxide (indium doped tin
oxide) was coated. Drying and pressing were performed to form a
porous membrane including TiO.sub.2. The porous membrane had a
thickness of 0.035 mm.
[0132] The first electrode on which the porous membrane was formed
was dipped in a 0.3 mM ruthenium
(4,4-dicarboxyl-2,2'-bipyridine).sub.2(NCS).sub.2 solution for 24
hours to adsorb the dyes on the porous membrane. The porous
membrane on which the dyes were adsorbed was washed with
ethanol.
[0133] The first polymer gel electrolyte composition was coated on
the first electrode including the porous membrane thereon to form a
first electrolyte layer. Volatile organic solvents in the first
polymer gel electrolyte composition were volatilized by drying
under vacuum.
[0134] The second polymer gel electrolyte composition was coated on
the first electrode including the first electrolyte layer thereon
to form a second electrolyte layer.
[0135] A transparent glass substrate having a substrate resistance
of 10 .OMEGA./.quadrature. on which indium tin oxide was coated was
deposited with platinum by sputtering to form a catalyst electrode
with a surface resistance of 0.5.OMEGA.. Thereby, a second
electrode was fabricated. Through-holes penetrating the second
electrode were formed by drilling with a bit having a diameter of
0.75 mm.
[0136] The electrolyte on the first electrode was arranged to face
the second electrode and then a 60 .mu.m-thick thermoplastic
polymer film was positioned between the transparent substrates of
the first and second electrodes. The first and second electrodes
were subjected to hot-pressing at 80.degree. C. for 9 seconds to
assemble the first and second electrodes.
[0137] Extra electrolyte was removed through the through-holes of
the second electrode and then the through-holes of the second
electrode were sealed to fabricate a dye sensitized solar cell.
COMPARATIVE EXAMPLE 1
[0138] 1.20M 1-propyl-3-methylimidazoliumiodide and 0.12M iodine
were dissolved in a solvent of poly(ethyleneglycol)dimethylether
(PEGDME, weight average molecular weight 250 /mol) to prepare a
mixed solution.
[0139] 30 wt % of TiO.sub.2 semiconductor particles having an
average particle diameter of 20 nm were dispersed in 100 ml of
acetylacetone to prepare a composition for a porous membrane. The
composition was coated using a doctor blade at a rate of 5 mm/sec
on a transparent glass substrate having a substrate resistance of
10 .OMEGA./.quadrature. on which indium tin oxide (indium doped tin
oxide) was coated. Drying and pressing were performed to form a
porous membrane including TiO.sub.2. The porous membrane had a
thickness of 0.035 mm.
[0140] The first electrode on which the porous membrane was formed
was dipped in a 0.3 mM ruthenium
(4,4-dicarboxyl-2,2'-bipyridine).sub.2(NCS).sub.2 solution for 24
hours to adsorb the dyes on the porous membrane. The porous
membrane on which the dyes were adsorbed was washed with ethanol to
prepare a light absorption layer.
[0141] A transparent glass substrate having a substrate resistance
of 10 .OMEGA./.quadrature. on which indium tin oxide was coated was
deposited with platinum by sputtering to form a catalyst electrode
with a surface resistance of 0.5.OMEGA.. Thereby, a second
electrode was fabricated. Through-holes penetrating the second
electrode were formed by drilling with a drill bit having a
diameter or 0.75 mm.
[0142] The light absorption layer on the first electrode was
arranged to face the second electrode and then a 60 .mu.m-thick
thermoplastic polymer film was positioned between the transparent
substrates of the first and second electrodes. The first and second
electrodes were subjected to hot-pressing at 80.degree. C. for 9
seconds to assembly the first and second electrodes. The
electrolyte prepared as above was injected into the through-holes
of the second electrode. The through-holes were sealed with a
thermoplastic polymer film and a cover glass to fabricate a dye
sensitized solar cell.
COMPARATIVE EXAMPLE 2
[0143] 1.20M 1-propyl-3-methylimidazolium iodide and 0.12M iodine
were dissolved in a solvent of poly(ethyleneglycol)dimethylether
(PEGDME, weight average molecular weight: 250 /mol) to prepare a
mixed solution. 10 wt % of silica nano-particles (average particle
diameter: 30 nm) (fumed silica, available from Aldrich, St. Louis,
Mo.) were added to the mixed solution and then dispersed by
agitating and ultra-sonication grinding to prepare a polymer gel
electrolyte composition having a viscosity of 3000 cP. Using the
polymer gel electrolyte composition, the dye sensitized solar cell
was fabricated according to the same method as in Comparative
Example 1.
COMPARATIVE EXAMPLE 3
[0144] 1.20M 1-propyl-3-methylimidazolium iodide and 0.12M iodine
were dissolved in a solvent of poly(ethyleneglycol)dimethylether
(PEGDME, weight average molecular weight: 250 /mol) to prepare a
mixed solution. 10 wt % of polyethylene oxide (weight average
molecular weight 1,000,000 g/mol) was added to the mixed solution
and then mixed by agitating and ultra-sonication grinding to
prepare a polymer gel electrolyte composition having a viscosity of
2000 cP. Using the polymer gel electrolyte composition, the dye
sensitized solar cell was fabricated according to the same method
as in Example 1.
COMPARATIVE EXAMPLE 4
[0145] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 750 g/mol was used.
COMPARATIVE EXAMPLE 5
[0146] The dye sensitized solar cell was fabricated according to
the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 1000 g/mol was used.
COMPARATIVE EXAMPLE 6
[0147] The dye sensitized solar cell was fabricated according to
the same method as in Comparative Example 1, except that 1.20M
1-propyl-3-methylimidazoliumiodide and 0.12M iodine were dissolved
in a solvent of poly(ethyleneglycol)dimethylether (PEGDME, weight
average molecular weight 400 g/mol) to prepare a mixed solution,
which was used as an electrolyte.
COMPARATIVE EXAMPLE 7
[0148] 1.20M 1-propyl-3-methylimidazolium iodide and 0.12M iodine
were dissolved in a solvent of poly(ethyleneglycol)dimethylether
(PEGDME, weight average molecular weight: 400 g/mol) to prepare a
mixed solution. 10 wt % of polyethylene oxide (weight average
molecular weight 1,000,000 g/mol) was added to the mixed solution
and then agitated to prepare a polymer gel electrolyte composition
having a viscosity of 2200 cP. Using the polymer gel electrolyte
composition, the dye sensitized solar cell was fabricated according
to the same method as in Example 1.
COMPARATIVE EXAMPLE 8
[0149] The polymer gel electrolyte composition was prepared
according to the same method as in Example 1, except that
poly(ethyleneglycol)dimethylether having a weight average molecular
weight of 750 g/mol was used.
[0150] 30 wt % of TiO.sub.2 semiconductor particles having an
average particle diameter of 20 nm were dispersed in 100 ml of
acetylacetone to prepare a composition for a porous membrane. The
composition was coated using a doctor blade at a rate of 5 mm/sec
on a transparent glass substrate having a substrate resistance of
10 .OMEGA./.quadrature. on which indium tin oxide (indium doped tin
oxide) was coated. Drying and pressing were performed to form a
porous membrane including TiO.sub.2. The porous membrane had a
thickness of 0.035 mm.
[0151] The first electrode on which the porous membrane was formed
was dipped in a 0.3 mM ruthenium
(4,4-dicarboxyl-2,2'-bipyridine).sub.2(NCS).sub.2 solution for 24
hours to adsorb the dyes on the porous membrane. The porous
membrane on which the dyes were adsorbed was washed with
ethanol.
[0152] The polymer gel electrolyte composition was coated on the
first electrode including the porous membrane thereon to form an
electrolyte layer.
[0153] A transparent glass substrate having a substrate resistance
of 10 .OMEGA./.quadrature. on which indium tin oxide was coated was
deposited with platinum by sputtering to form catalyst electrode
with a surface resistance of 0.5.OMEGA.. Thereby, a second
electrode was fabricated.
[0154] The electrolyte on the first electrode was arranged to face
the second electrode and then a 60 .mu.m-thick thermoplastic
polymer film was positioned between the transparent substrates of
the first and second electrodes. The first and second electrodes
were subjected to hot-pressing at 80.degree. C. for 9 seconds to
assembly the first and second electrodes.
[0155] The dye sensitized solar cells according to Example 1 and
Comparative Example 8 were evaluated in terms of electrolyte
filling. The evaluation results are shown in FIGS. 3A and 3B.
[0156] FIG. 3A is a photograph of electrolyte filling in the solar
cell according to Example 1, and FIG. 3B is a photograph of
electrolyte filling in the solar cell according to Comparative
Example 8. The reference numeral 16 denotes a through-hole of the
second electrode.
[0157] As shown in FIGS. 3A and 3B, in the solar cell according to
Example 1, excessive electrolyte was removed through the
through-hole penetrating the second electrode and thereby the
polymer electrolyte was completely filled to implement complete
adherence between the electrolyte and the second electrode. On the
contrary, in the solar cell according to Comparative Example 8
without a through-hole, electrolyte was not completely filled to
implement incomplete contacting between the electrolyte and the
second electrode.
[0158] Ion conductivity (mS/cm), open voltage (V), short-circuit
current (mA/cm.sup.2), fill factor (%), and photovoltaic efficiency
(%) of the solar cells according to Examples 1 to 3 and Comparative
Examples 2 to 5 were measured. The measurement results are shown in
the following Table 1.
[0159] Herein, a xenon lamp of Oriel, 01193 (available from Newport
Corp., USA), was used as a light source, and the solar condition
(AM 1.5) of the xenon lamp was corrected by using a standard
photovoltaic cell (Frunhofer Institute Solare Engeriessysteme,
Certificate No. C-ISE369, Type of material: Mono-Si+KG filter).
[0160] The fill factor is a value obtained by dividing
Vmp.times.Jmp, where Vmp is a current density and Jmp is a voltage
at a maximal electric power voltage, by Voc.times.Jsc. The
photovoltaic efficiency (.eta.) of a solar cell is a conversion
efficiency of solar energy to electrical energy, which can be
obtained by dividing a solar cell electrical energy
(current.times.voltage.times.fill factor) by an energy per a unit
area (P.sub.inc) as shown the following Equation 1.
.eta.=(VocJscFF)/(P.sub.inc) Equation 1
wherein the P.sub.inc is 100 mW/cm.sup.2 (1 sun).
TABLE-US-00001 TABLE 1 Weight average molecular Particle weight of
the diameter of first polymer inorganic Short- or liquid nano- Ion
Open circuit Fill compound particles conductivity voltage current
factor Efficiency (g/mol) (nm) (mS/cm) (V) (mA/cm.sup.2) (%) (%)
Ex. 1 250 30 0.16 0.78 14.98 66.7 7.79 Ex. 2 500 30 0.11 0.74 14.21
67.5 7.10 Ex. 3 88.1 30 0.21 0.76 15.32 65.5 7.81 Comp. 250 30 0.11
0.75 10.24 69.9 5.36 Ex. 2 Comp. 250 -- 0.06 0.71 9.68 71.2 4.89
Ex. 3 Comp. 750 30 0.08 0.65 13.05 63.2 5.36 Ex. 4 Comp. 1000 30
0.05 0.62 9.44 54.8 3.21 Ex. 5
[0161] As shown in Table 1, the solar cells including the
electrolyte according to Examples 1 to 3 show excellent cell
characteristics compared those of Comparative Examples 2 to 5. The
solar cells according to Comparative Examples 4 and 5 including the
first polymer having a weight average molecular weight of more than
500 mg/mol show lower characteristics. These results indicate that
the characteristics of the first polymer have a large effect on
cell characteristics.
[0162] The solar cell according to Example 1 including the polymer
gel electrolyte that is composed of the first polymer, the second
polymer, and the TiO.sub.2 nano-particles shows high ion
conductivity and short-circuit current compared to the solar cell
according to Comparative Example 2 including the polymer gel
electrolyte where the first polymer was gellized by addition of
silica nano-particles. These results are caused by the fact that
the silica nano-particles for a gelling agent lower gelation of an
electrolyte due to weak particle interactions and electrolyte ion
conductivity is deteriorated by gelation. The TiO.sub.2
nano-particles in Example 1 have more advantages in improvement of
ion conductivity and light-scattering effect than the silica
nano-particles in Comparative Example 2.
[0163] The cross-sections of the porous membranes of solar cells
according to Example 1 and Comparative Example 4 were evaluated by
SEM photography. The results are shown in FIGS. 4A and 4B.
[0164] FIG. 4A is a SEM photograph showing a cross-section of a
porous membrane in which an electrolyte is filled in the solar cell
according to Example 1. FIG. 4B is a SEM photograph showing a
cross-section of a porous membrane in which an electrolyte is
filled in the solar cell according to Comparative Example 4.
[0165] As shown in FIGS. 4A and 4B, as the weight average molecular
weight of the first polymer becomes larger, viscosity increases. As
the molecule size increases, the electrolyte incompletely invades
into the nanopores of the porous membrane and electrolyte ion
conductivity decreases.
[0166] In order to evaluate solar cell characteristics depending on
the addition of the inorganic nano-particles and the average
particle diameter of the inorganic nano-particles, open voltage
(V), short-circuit current (mA/cm.sup.2), fill factor (%), and
efficiency (%) of the solar cells according to Examples 2 and 4 to
9 and Comparative Example 3 were measured. The results are shown in
the following Table 2.
TABLE-US-00002 TABLE 2 Particle Short-circuit diameter Open current
Fill factor Efficiency (nm) voltage (V) (mA/cm.sup.2) (%) (%) Ex. 2
30 0.74 14.21 67.5 7.10 Ex. 4 30 0.69 13.20 70.8 6.44 Ex. 5 30 0.72
13.15 71.9 6.77 Ex. 6 180 0.73 12.97 75.0 7.07 Ex. 7 10 0.72 11.80
72.8 6.89 Ex. 8 100 0.72 13.35 73.1 7.03 Ex. 9 1000 0.75 8.17 72.0
4.41 Comp. -- 0.71 9.68 71.2 4.89 Ex. 3
[0167] As shown in Table 2, the solar cells according to Examples 2
and 4 to 9 including a polymer gel electrolyte in which various
inorganic nano-particles are added show excellent cell efficiency
compared to that of Comparative Example 3 including a polymer gel
electrolyte without inorganic nano-particles.
[0168] The results also show that short-circuit currents are
changed depending on the average particle size of the TiO.sub.2
nano-particles. For example, the solar cell according to Example 9
including 1000 nm TiO.sub.2 particle shows significantly increased
short-circuit current due to decreased specific surface area of the
particles.
[0169] The solar cell according to Example 7 including TiO.sub.2
particles having a particle diameter of less than or equal to 10 nm
also shows slightly decreased short-circuit current due to decrease
of light-scattering effect even though short-circuit current
increases due to increase of specific surface area. These results
indicate that the inorganic nano-particles having an average
particle diameter of less than 1 .mu.m may preferably be used.
According to one embodiment, the inorganic nano-particles may have
an average particle diameter of more than or equal to 10 nm and
less than 1 .mu.m.
[0170] In order to evaluate cell characteristics depending on the
amount of the inorganic nano-particles, open voltage (V),
short-circuit current (mA/cm.sup.2), fill factor (%), and
efficiency (%) of the solar cells according to Example 10 to 16
were measured as above. The results are shown in the following
Table 3.
TABLE-US-00003 TABLE 3 Amount of titanium oxide Short-circuit Fill
nano-particles Open current factor Efficiency (wt %) voltage (V)
(mA/cm.sup.2) (%) (%) Ex. 10 wt % 0.74 17.28 69.5 8.8 10 Ex. 1 wt %
0.72 17.97 66.2 8.6 11 Ex. 5 wt % 0.71 20.62 65.2 9.5 12 Ex. 20 wt
% 0.69 19.84 66.1 9.0 13 Ex. 30 wt % 0.64 13.62 61.2 5.3 14 Ex. 15
wt % 0.70 18.11 69.8 8.9 15 Ex. 40 wt % 0.62 11.94 60.2 4.5 16
[0171] As shown in Table 3, when the titanium oxide nano-particles
were used in an amount of 1 to 30 wt %, efficiency is more
improved. When the titanium oxide nano-particles are 5 wt %,
efficiency is most improved. Example 16 including 40 wt % of
titanium oxide nano-particles shows a significant short-circuit
current decrease and thereby deteriorated efficiency. These results
indicate that the extra amount of the inorganic nano-particles in
the electrolyte cell reduce ion amount filled in the electrolyte,
and thereby oxidation-reduction reactions of the solar cell do not
occur smoothly.
[0172] In order to evaluate photovoltaic efficiency of the solar
cells according to Example 17 and Comparative Examples 6 and 7,
photoelectric current-voltage was measured. From the measured
photoelectric current-voltage curved line, a short-circuit current,
an open voltage, a fill factor, and photovoltaic efficiency were
calculated. The results are shown in FIG. 5 and the following Table
4.
TABLE-US-00004 TABLE 4 Short-circuit current Open voltage Fill
factor Efficiency (mA/cm.sup.2) (V) (%) (%) Ex. 17 14.55 0.72 68.3
7.19 Comp. Ex. 6 17.15 0.64 63.4 6.92 Comp. Ex. 7 9.15 0.75 74.6
5.11
[0173] FIG. 5 shows photoelectric current-voltage characteristics
of the solar cells according to Example 17 and Comparative Examples
6 and 7.
[0174] As shown in Table 4 and FIG. 5, the solar cell according to
Comparative Example 7 including a polymer gel electrolyte shows
significantly low current and photovoltaic efficiency. On the
contrary, the solar cell according to Example 17 including a
polymer gel electrolyte where titanium oxide inorganic
nano-particles are further added shows a better current and more
improved efficiency compared to the solar cell according to
Comparative Example 6 including a liquid electrolyte.
[0175] Photocharge efficiency (IPCE: incident photon-to-current
efficiency) of the solar cells according to Example 17 and
Comparative Examples 6 and 7 were measured. The results are shown
in FIG. 6.
[0176] As shown in FIG. 6, the solar cell according to Comparative
Example 7 including the polymer gel electrolyte turned out to have
a low IPCE compared to the solar cell according to Comparative
Example 6 including the liquid electrolyte. This result is caused
by the fact that the solar cell according to Comparative Example 7
includes a polymer besides a liquid electrolyte to be gellized
resulting in decrease of ion conductivity and current generation.
On the contrary, the solar cell according to Example 17 including
the titanium oxide inorganic nano-particles in the polymer gel
electrolyte shows increase of ion conductivity due to addition of
the titanium oxide and thereby increase of current generation. The
titanium oxide inorganic nano-particles also increase IPCE at a
long wavelength due to a light scattering effect.
[0177] With respect to the solar cells according to Example 17 and
Comparative Examples 6 and 7, current-potential was measured. From
the measurement, ion diffusion coefficient (D.sub.app) was
calculated by Equation 2. The results are shown in FIG. 7.
Dapp = Iss 4 ncaF Equation 2 ##EQU00001##
[0178] Wherein, in Equation 2, I.sub.ss is a current at a normal
state, n is a number of transferred electrons per molecule, c is
concentration, a is diameter of a platinum microelectrode, and F is
a Faraday constant.
[0179] As shown in FIG. 7, in the case of the solar cell according
to Comparative Example 7, the ion diffusion coefficient
significantly decreases due to an increase of viscosity. However,
in the case of the solar cell according to Example 17 including the
titanium oxide inorganic nano-particles added to the electrolyte,
the ion diffusion coefficient is restored to an equivalent of the
liquid electrolyte according to the electrolyte according to
Comparative Example 6.
[0180] Open voltage (V), short-circuit current (mA/cm.sup.2), fill
factor (%), and efficiency (%) of the solar cell according to
Example 10 were measured according to the same method as above, and
were compared to the results of the solar cell according to
Comparative Example 1. The results are shown in the following Table
5.
TABLE-US-00005 TABLE 5 Open voltage Short-circuit current Fill
factor Efficiency Electrolyte (V) (mA/cm.sup.2) (%) (%) Comp. Ex. 1
0.78 15.28 66.2 8.2 Ex. 10 0.74 17.28 69.5 8.8
[0181] As shown in Table 5, the solar cell according to Example 10
shows higher efficiency that that of Comparative Example 1
including the liquid electrolyte. In the case of the solar cell
according to Example 10, the titanium oxide inorganic
nano-particles improve electrolyte ion conductivity even though
gelation is performed by addition of the polymer.
[0182] From these results, it can be seen that the inorganic
nano-particles added to the polymer gel electrolyte improve cell
efficiency by about 4% compared to a liquid electrolyte, and endows
excellent durability.
[0183] The photocharge efficiency changes (IPCE: incident
photon-to-current efficiency) of the solar cells according to
Example 10 and Comparative Example 3 were measured. The results are
shown in FIG. 8.
[0184] As shown in FIG. 8, the solar cell according to Comparative
Example 3 including the polymer gel electrolyte shows lower. IPCE
than that of Example 10 because of the gelation of the polymer
added in the liquid electrolyte resulting in a decrease of ion
conductivity and current generation. However, the titanium oxide
inorganic nano-particles added in the polymer gel electrolyte of
the solar cell according to Example 10 increase ion conductivity,
and thereby increases current generation. The titanium oxide
inorganic nano-particles also increase IPCE at a long wavelength
due to a light scattering effect.
[0185] Efficiency decrease (decrement) during operations of solar
cells according to Example 10 for 60 days was measured. The
normalized efficiency is obtained by percentage of measured
efficiency with respect to the initial efficiency by the following
Equation 3. The results are shown in FIG. 9.
NormalizedEfficiency = MeasuredEfficiency InitialEfficiency .times.
100 Equation 3 ##EQU00002##
[0186] As shown in FIG. 9, the normalized efficiency of the solar
cell including the polymer gel electrolyte according to Example 10
does not decrease.
[0187] Open voltages (V), short-circuit currents (mA/cm.sup.2),
fill factors (%), and efficiency (%) of the solar cells according
to Examples 10 and 18 were measured according to the same method as
above. The measurement results are shown in the following Table
6.
TABLE-US-00006 TABLE 6 Open voltage Short-circuit current Fill
factor Efficiency Electrolyte (V) (mA/cm.sup.2) (%) (%) Ex. 10 0.74
17.28 69.5 8.8 Ex. 18 0.75 18.13 68.9 9.4
[0188] As shown in Table 6, the solar cell according to Example 18
shows higher efficiency that that of Example 10 including the gel
electrolyte. In the case of the solar cell according to Example 18,
polymer solutions having various viscosities are sequentially
coated to improve assembling properties between the first and
second electrodes. As a result, the solar cell according to Example
18 shows higher efficiency. In the foregoing discussions, those
referred to as comparative examples do not necessarily represent
prior art and the term "comparative example" does not constitute an
admission of prior art.
[0189] The electrolyte composition for a dye sensitized solar cell
according to one embodiment has improved ion conductivity and
enhances cell stability and durability when it is applied to a dye
sensitized solar cell.
[0190] While the instant disclosure has been described in
connection with what is presently considered to be practical
exemplary embodiments, it is to be understood that the disclosure
is not limited to the embodiments, but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *